Method and apparatus for the combustion of hydrogen sulfide and the production of sulfur



May 27, 1958 M. J. HOFSTEDE 2,836,481

METHOD AND APPARATUS FOR THE COMBUSTION OF HYDROGEN SULFIDE AND THE PRODUCTION OF SULFUR 2 Sheets-Sheet 1 Filed March 3, 1952 l AIR PILOT Inventor: Mcrinus J. Hai'sndz W-W/ 4%Pfl His Afiormg May 27, 1958 M. J. HOFS'TEDE 2,836,481

METHOD AND APPARATUS FOR THE COMBUSTION OF HYDROGEN SULF'IDE AND THE PRODUCTION OF SULFUR Filed March 3, 1952 2 Sheets-Sheet 2 Fig.3

/7. 37% His AH'ornzg Patented May 27, 1958 METHOD AND APPARATUS FOR THE COMBUS- TION F HYDRGGEN SULFLDE AND THE PRO- DUCTISN 0F SULF Marinns J. Hofstede, Delft, Netherlands, assignor to Shell Development Company, Emeryviiie, Cali, 2 corporation of Delaware Application March 3, 1952, Serial No. 274,632

Claims priority, application Netherlands March 6, 1951 6 Claims. (Cl. 23--225) This invention relates to toe combustion of hydrogen sulfide with regulated amounts of an oxygen-containing gas, and may be applied, for example, to the production of sulfur by burning hydrogen sulfide with a limited amount of an oxygen-containing as such as air, air enriched with oxygen, such as low purity oxygen, or low purity oxygen itself. The invention may be applied to hydrogen sulfide that is substantially pure or to a gas that contains hydrogen sulfide in appreciable concentrations; and the amount of oxygen may be such as to procure the greatest yield of elemental sulfur or it may be selected with a view to producing combustion products of some other desired combustion, e. g., suitable for fur ther combustion after further addition of an oxygen-containing gas.

In industry the combustion of hydrogen sulfide with air or oxygen, either to form sulfur according to the equation H S+ /2O ==H O+S, or to S0 according to the equation H S+1 /2O =II O+SO is usually effected by means of burners operating on the principle of the Bunsen burner. In such operations the sulfuretted hydrogen is mixed with a part of the quantity of combustion air required in a mixing tube joined to an injector. At the end of this tube the mixture formed is burnt with a further supply of air to the desired end products. Burners of this type produce long flames, indicating that the combustion proceeds very slowly, so that the combustion temperature is lower than that which would be attainable should the combustion proceed more rapidly and, consequently, within a smaller space. in order to effect an improvement in these respects, the flame is surrounded by a cylindrically-shaped combustion chamber made of refractory material; this expedient, however, only partly removes the objections. For a fully satisfactory operation, it is necessary to arrange for (1) an intensive mixing of the hydrogen sulfide with the total quantity of air or oxygen required and (2) a rapid combustion of the mixture thus formed. When a combustible mixture of the correct composition is formed, its explosivity constitutes a source of danger, so that care should be taken that the flame cannot flash back from the combustion space to the supply conduit or source of the gas mixture; with the ordinary burners of the Bunsen type, it was difficult to devise means of preventing the flame from flashing back.

If, as is usually the case, the hydrogen sulfide contains hydrocarbons, such as methane, ethane or ethylene, even to only a fairly small percentage, e. g., from 0.5 to 2 percent, and it is desired to burn the hydrogen sulfide in a limited amount of oxygen to produce sulfur, it has been found that with the installations as commonly used a coke-like product is formed as a result of incomplete combustion of the hydrocarbon gas, which product is deposited on the burner nozzle and other parts of the equipment. Further, soot-like particles which are formed by the incomplete combustion find their way to the combustion gases and give a greenish color to the sulfur and the market price of the sulfur.

2i when the latter is condensed, thereby lowering the quality Hence, it is desirable to improve the combustion so as to convert these hydrocarbons to water and carbon monoxide or dioxide without the formation of coke or soot.

Finally, the intensification of the combustion favorably affects the percentage of the hydrogen sulfide that can be ultimately converted. For, if the combustion proceeds rapidly and in a fairly sharply defined zone, the combustion gases can be rapidly cooled or quenched in a subsequent zone without adversely affecting or interrupting the combustion, and by means of the rapid cooling it is possible to suppress to a great extent reactions which occur at lower temperatures and which cause retrograde formation H 8.

A principal object of the invention is to effect an intensification of the combustion of hydrogen sulfide by means of which the advantages described above can be achieved. Further objects are to provide an improved apparatus and method for producing elemental sulfur in high yield from hydrogen sulfide.

.In summary, according to the present invention the hydrogen sulfide is mixed intensively with all of the oxygen-containing gas which is required for the desired reaction preliminary to combustion and the mixture thus formed is discharged into a combustion chamber with a rotating movement as an annular current at a high forward velocity sufficient to prevent flash-back through an annular slot in the rear wall of the chamber. The combustion chamber has an open front end and a confined side wall with a length at least equal to 0.8 times the inside diameter of the side Wall near the front end and is preferably shaped as a surface of revolution, whereby stabilizing vortices of fiame gases are formed both within said annular current and between the annular current and the side wall of the combustion chamber for rapidly heating the mixture emerging from the slit and promoting rapid combustion. The products of combustion are discharged from the open end of the combustion chamber and may then be rapidly cooled to prevent undesired reactions and to condense sulfur formed in the combustion which sulfur may be separated from the gases by any desired technique, such as the use of cyclones or scrubbing with a water spray or with cooled, molten sulfur, or a combination of such steps.

A combustion chamber which has a sufficient length in relation to the diameter to form stabilizing fiame vortices when a combustible mixture is supplied through an annular slot in the rear wall is described in U. S. Patent No. 2,515,845; double vortices and fiow patterns used in the instant process are those indicated in Figure 3 of that patent and the dimensions disclosed therein may be used to determine the suitable dimensions for the combustion chamber. While the patent indicates only minimum lengths for the combustion chamber, it is in general preferred to use combustion chambers that are not longer than 1.5 times the diameter at the front end, e. g., between 0.9 and 1.2 times such diameter.

A further feature of the invention is the arrangement of the combustion chamber to provide a pilot flame that emerges forwardly from the rear wall of the chamher at the central longitudinal axis, and in the method of insuring prompt ignition of the hydrogen sulfide mixture by the use of this pilot flame. In constructing this burner the strongly corrosive character of the hot mixture occurring in the combustion chamber should be taken into account; for this reason the presence of uncooled metal parts in the wall of the combustion chambet or exposed to such mixture should be avoided. Consequently, the opening for the pilot flame should not be provided with an uncooled metal lining. The

fere'ntial'direction to an annular position of this flame is of great importance for the proper functioning of the burner; it should be located in the axis of the combustion chamber, thus in the center of the annular slot through which the.hydrogensulfide mixture enters the combustion'chamber. By means of of carbon in .the centerjof the burner is completely avoided.

The invention will be described more particularly by reference to the accompanying drawings forming a part of this specification and illustrating one preferred embodiment, wherein:

,Figure 1 is a rear'elevation view of the burner, partly in section, showing the mixing device;

Figure 2 is a longitudinal section through the burner on an enlarged scale, takenon line 22 of Figure l; Figure'3 is an enlarged'vertical longitudinal sectional view of the'front end of the 'pilot flame tubes; and V Figure .4 is a diagrammatic representation of a sulfur plant showing the relation of the burner and burning step to the other operations. 7

Referring'to the drawings in detail, the apparatus may comprise a mixer of any suitable design, such as an sulfide is' admitted from an 'inlet l1; and to the nozzle 12'of which air or some other oxygen-containing gas is I admitted from an inlet 13. 1 It will be understood that the iuspirator '10 shown is merely" representative of various types of suitable mixing devices wherein one or' both of the inlets may be provided with suitable fans 'for inducing flow'and with flow control means for maina small excess of air in the pilot flame the deposition noted that the opening 22 in the block is flared gradually toward the rear and that the plug 23 is enlarged toward the rear with a complementary rounded :shape, whereby the slit2-t is in communication with the annular whirl chamber 37 by a smooth channel, the walls of which have surfaces of revolution, the channel commencingat the periphery of the disc 28, and decreasing in radiustowardthe slit 24. The rear, enlarged part of the plug 23 fits within the sleeve 26 and is positioned axiallywith respect theretoby engagement with an' in-' ward Zn) on the sleeve and by a ring 31'.

Theplug is formed to provide a pilot flame. To this end it has a central bore 32 which is counterbored from the' rear to receive an air tube 33 which extends rear: wardly through the rear plate at which ajferrule 34 is provided. A T-fltting 35 at the rear end of the air 7 tube provides a lateral opening through which air may 'ibe. admitted. Supported concentrically within the air injector ill) to the housing of which gaseous hydrogen a tube by means of a plug 36 is a gaseous fuel tube 37 through which a combustible gas may be admitted, It will bev notedthat the tubes and 37 do not extend forwardly to the front of the plug 23 but terminate at isome distances from the rear wall of the combustion chamber, so that they are not exposedto the strongly corrosive effects of the gases present in this chamber. If desired, a burner nozzle 38 can be mounted at' the front end of the tube 33' for effecting combustion within.

I, the bore 32 in a manner that the flame cannot be blown off by turbulence occurring wvithin the combustion;

taining the volumetric ratio of the hydrogen sulfide'and.

the oxygen-containing gas in the resulting mixturefat constant, desired value, despite varying pressures of the gases, Such pressurizing and controlling means" per se being familiar, tothose skilled in the art, they are not illustratedin the drawings. 'The gases are mixed in the mixing tube 14 and the resulting gaseous mixture is which are connected tangentially in a common circumciated with the burner.

' The burner comprises a block 18 of refractory material whichi'shollow to provide a combustion chamber 19, the'side wall 26 of which is shaped as a surface of revolution and. is substantially tubiform, that is, it does. not diverge greatly. toward the front, being substantially cylindrical or flaring slightly as shown. length of the side wall should in most cases be: at least 0.8 times the diameterat'the open, front end, lengths not greater th'an'lS times the diameter being preferred.

The combustion chamber'has'a rear'wall that consists in part of an annular part 21 that surrounds a circular 'opening zz 'formed coaxially'with the chamber and. in part of the forward face'of a plug. 23 which may, if

desired, be formed separate from the block ifi The forward part. of the plug a3 is exteriorly cylindrical with adiarneter less than that of the opening '22 was to provide'an annular slot 24 through'which the aforesaid gaseous mixture can be; discharged ferwardly into the combustion chamber. It is advantageous to make the diameter of the opening 22 equal to about 0.15 to 0.67

are connected tangentially, an inner cylindrical sleeve;

The

' divided equally among a plurality of conduits 15,16,

whirl chamber 17 assoi,

chamber. This nozzle, when'provided, is located at a sutliciently great distance from the rear wall of the combustion chamber to avoid exposure to the corrosive action of the gases. As shown in greater detail in Fig. 3, this nozzle has a tubular, externally threaded body -which is threaded intothe front end of the tube 33; an annular, radialfiange 39 at the front; and a frusto-conical;

forwardly converging flange 4% toward the rear'pro ivided with perforations 41'. The tube 37 terminates some distance back from the nozzle to permit the gaseous fuel and'airtornix. During 'operation'the flame commencesin rear of the flange 4i and most. of it issues through the central opening within the flange 49; how- -ever, some flame flows throughthe openings 41 and a pocket of flame is retained in the annular space bef 'tween' the flanges 39 and 4%) which serves to 'r e-ignite the pilot flame in the event of a blow-out. The. pilot flame can be ignited initially through a lighter hole 42 which is formed in the block id and is normally closed by a' ceramic plug 43. it has been found thatthe choice i of the position of the pilot, flameis very important; if this pilot flame is located at a place other than in the c'enterof rear wall of the combustion chamber, it is.

easily blown oil by the violent current of air should the supply of hydrogen sulfide be interrupted. 7 j

The center portion of the rear wall 21 of the combustion chamber, i. e; the front'part 'of the plug 23 and f wall 29 atthe rear of the r the part surrounding the annular slit 24 may be formed "of a metal such'as steel, provided such parts can be effectively cooled by the circulation of a cooling medium such as a cooling liquid to a and 500 centigfade. V V As shown in Fig. 4, the b'urner can be mounted ad temperature. between jacent to anysuitable unit for immediately'cooling the combustion gases, "ljhis 'tunit ma'y, take the form of a waste he at recovery plant, such as the steam boiler 44 having a bundle of tubes. 45 extending. between, tube,

, sheets ddand'made oficorrosion resistant steel. Water K admitted; through inlet 47; is heatedand may be with drawn as steam through outlet 43; Sulfurcondensed; within the boiler can b'e Withdrawn as a liquid through a asseesi sulfur. For example, this outlet may be connected to the bottom of a contact tower 54 having spray nozzles 55 at the top to which a coding medium, such as a suitable liquid may be supplied. In the embodiment shown, wherein sulfur is used as the cooling and scrubbing liquid, the tank Stl is connected by a pipe 56 to the suction side of a pump 57 which discharges through a pipe 58 which is provided with a valve 59 and extends through a heat exchanger 66 to which cooling water may be admitted for indirect heat exchange with the sulfur. The bottom of the tower is connected by a drain line 61 to the collecting tank 59.

The gas outlet 63 may be connected to a suitable stack for venting the gases to the atmosphere or to a further treating unit, as desired.

Operation The method and apparatus can be applied to hydrogen sulfide in varying degrees of purity. When applied to the production of elemental sulfur of high purity, it is desirable to use a hydrogen sulfide gas wherein hydro carbons, if any, constitute less than and, preferably, less than 3% by volume of the combustibles, which usually consist mainly of hydrogen sulfide but may additionally contain hydrogen in amounts minor in relation to the hydrogen sulfide. The gas may consist substantially wholly of hydrogen sulfide and other combustibles or may contain varying amounts, e. g., up to 30- 70% of incombustible gases, such as carbon dioxide nitro gen, etc. The composition will depend upon the source of the hydrogen sulfide and the method used in concentrating it; for example, a typical hydrogen sulfide gas obtained by solvent extraction from petroleum refinery gases contains between 88 and 96% H 8, between 5 and 10% CO and between 0.5 and 3% of gaseous hydrocarbons usually containing one or two carbon atoms, all percentages being by volume. Such concentrated hydrogen sulfide may be burned to form sulfur employing atmospheric air as the oxygen-containing gas, but low purity ox gen or air enriched with low purity oxygen may be employed, particularly when the hydrogen sulfide gas contains large amounts of incombustibles and/or when it is desired to avoid too great a dilution of the gas in cases where the hydrogen sulfide is subjected to successive combustions, as described hereinafter.

The hydrogen sulfide gas and the oxygen-containing gas, such as air, are admitted through the inlets 11 and 13, respectively, in regulated proportions to produce a combustible mixture suitable for use in the burner. The pressure of this mixture may, for example, be about 10 to 20 inches of water gauge, although considerably higher pressures may be employed, and the ratio of oxygen to hydrogen sulfide will depend upon the specific object of the oxidation reaction. Thus, in one aspect, the invention is concerned with the conversion of hydrogen sulfide to sulfur in the combustion step, and in this case the volumetric ratio of oxygen to hydrogen sulfide is usually less than 1, e. g., it may be held between about 0.3 and 0.7. When it is desired to produce the maximum quantity of elemental sulfur in a single combustion step within the combustion zone 19, the volumetric ratio of oxygen to hydrogen sulfide is advantageously held close to 0.5, e. g., within the range 0.4-5 to 0.55 (corresponding to from about 2.15 to 2.62 volumes of atmospheric air per volume of hydrogen sulfide), values within the upper portion of the range or slightly above this range being preferably selected when the hydrogen sulfide gas contains up to 3% or a greater proportion, respectively, of hydrocarbons. However, in another aspect the invention resides in the technique of intimately mixing at below combustion temperature essentially all the hydrogen sulfide gas and oxygen-containing gas in proportion to produce a combustible mixture, said proportions being selected with a view to producing combustion products of any desired composition, e. g., containing either less or more oxygen than was indicated above, and of .burn' ing such mixture by feeding it in the manner described herein into a combustion zone wherein stabilizing vortices etfect rapid heating of the mixture and rapid combustion thereof while preventing flash-back from the com bustion zone toward the mixing zone. In such cases the preferred composition for the hydrogen sulfide gas above stated may not apply, and a greater concentration of hydrocarbons may be permissible. v I

The conduits 15 and 16, or at least the parts thereof connected to the whirl chamber 17, are small enough to discharge the gaseous mixture into the chamber with a sufiicient peripheral velocity to create a high rotational velocity about the central burner axis; this causes an even more intensive mixing than that previously effected in the injector 1t) and tube 14. From the whirl chamher the rotating, annular gas mixture flows through the annular chamber between the disc 28 and plate 29 into the annular slit 24, assuming first a spiral-like motion which changes into a substantially helical motion. The disc 28 aids in causing only properly mixed gases to enter this channel. Due to the reduction in the radius the angular or rotational velocity of the gas mixture increases toward the slit 24. The width of this slit is so chosen, in relation to the volumetric flow rate, that the gaseous mixture has a forward velocity exceeding the propagation velocity of the combustion of the mixture, whereby the flame is prevented from flashing back into the whirl chamber and the mixing tube.

The pilot'flame having been initially lit by inserting a match through the opening 42 and supplying a combustible gas and air through the tubes 33 and 37, respectively, the combustible hydrogen sulfide mixture ignites upon emerging from the slit 24 to form the main flame. The pilot flame is kept burning continuously, so that in the event of the main flame being extinguished, for instance, owing to a temporary interruption in the supply of hydrogen sulfide, it is immediately reignited upon resumption of the supply of hydrogen sulfide. Hence, it is impossible for an explosive mixture to accumulate in the combustion chamber 19 and the adjoining parts of the installation. It has been found that by locating the pilot flame at the vortex axis, as described, it will not be blown out by the violent air currents that occur in the combustion chamber particularly when the supply of hydrogen sulfide is interrupted. It has, moreover, been found that if a slight excess of air is supplied to the pilot flame, this flame prevents the formation of coke or soot particles from the hydrocarbons which are present in the hydrogen sulfide mixture supplied from the whirl chamber, even if the oxidation of the hydrogen sulfide mixture is very incomplete due to the use of limited amounts of oxygen for the purpose of producing sulfur. The amount of the excess air supplied to the pilot flame will depend upon the desired reaction and the amount of hydrocarbon gas present in the hydrogen sulfide mixture and may, for example, be about 5% to 50% by volume, based on the requirements for the pilot flame, or 0.02% to 3% by volume, based on the hydrogen sulfide, but the invention is not limited to these ranges.

The ignited rotating and forwardly advancing annulus of the hydrogen sulfide mixture expands due to centrifugal forces. The shape of the combustion chamber is such that, as indicated in the drawing, both inside and outside of the emerging annulus, torus-like vortices or whirls of flame gases are formed, as indicated at 65 and 66, respectively. These annular vortices may extend close to the slit 24 in the rear of the combustion chamber. Both vortices, and particularly the outer vortex 66, lead already burning mixture back to the place where ignition of the newly admitted gaseous mixture takes place and thus promotes rapid heating and ignition of the mixture and continued mixing. Furthermore, the well of the combustion chamber, which is hot when the ly of methane, and with '::,35.% H S was converted I 79 %.=Sulf1u' condensed from the'coinbustion and "the'combustion chamber were'iree from soot and coke.

burner is in operation, imparts heat to the fresh mix- 'ture' by radiation;

The intimate ,mixing of the hydrogen sulfide and oxygen both prior to introduction into the combustion of the sulfur present in the hydrogen suit dc is liberated The combustion gases'leavmg the as elemental sulfur. combustion chamber can be cooled'in any suitable coolingunit, such as'the waste heat boiler 44, which cooling V 7 should proceed as rapidly as possible, in order to prevent V side-reactions in which the sulfur is caused to form hydrogen sulfide. it is preferred to cool the gases sufficiently to condense a major part of the sulfur in the steam boiler and recover it throughthe drain 49. How ever, under certain conditions the boiler may be operatedat ahigher'temperatureat which little or no con-'iensation of sulfur is effected and the gases leaving by out let 53 contain most or all of the sulfur. cooled gases are further cooled in the tower 54 to which cooled, liquid sulfur is admitted at the top at a rate to condense most or substantially all of the sulfur vapor; the rate'is advantageously controlled by the valve 59 and the temperature is regulated by the flow of cooling water to the cooler 69. Molten sulfur is fed by the drain, pipe 62 to the tank 50 where it is 'c'ommingled with the sulfur recovered in the boiler a The gases withdrawn at the outlet as may still contain a certain quantity of hydrogen sulfide or other sulfur components, depending upon the quantity of air admitted to the feed stream. These gases can befurther processed to produce sulfur in a furnace filled with a catalyst; or, depending on the circumstances prevail ing, the gases may be allowed to escape to the atmosphere, the latter-occurring after combustion of the hydrogen sulfide to sulfurjdioxide if avoidance of discharge 'of H Sis required; or the gases can be used for the produc- The partly asaeasi Iclaimas my invention: p L'A process for the productionof sulfur .from a1 gaseous mixture containing hydrogen sulfide as the major" combustible'and containing'n'ot more than about 7 by volume of said gaseous mixture of hydrocarboniina: terials, said process comprising the steps of continuousof said zone at which, said oxygen-containing mixture enters, a pilot flame directed in the same direction as p the. oxygen-containing mixture is fiowing, said pilot flame 1 ti'on of sulfur dioxide or sulfuric acid. Moreover, theexit gases, when they contain hydrogen sulfide, maybe further mixed with an oxygen containing gas and subjected to further combustionfin the manner. described above,' employing for this purposetwo ormore systems'ofthe type indicated in Figure 4 wither without the tower 54, arranged as a series and recovering sulfur in such a process it is desirable to; operin each stage. ate the first mixer and burner a lower ratio of oxygento hydrogen sulfide than given above; e. volumes of oxygen for every volume of'hydrogen.

tide and oxygen'with the inert gases, particularly nitro gen, in the subsequent burner or burners, it'is desirable to use air enriched with oxygen or oxygen alone in one or more stages. a t

composition on a volumetric basis: 7

H 8: 90-95%; average 93% C0 540% average 6% C l-I 0.5 2%;-average 1% 1 V This gas, was mixed withair, the supply of which was maintained at between 2.34 and 2.40 volumes of air for 1 volume of H 3. The. burner was operated at varying loads near capacity; Thepilot flame was supplied with abouflOlcu. ft. per hour refinery gases, consisting large- 30% 5 air.

, with an average of e'. to sulfur From 71' to g.,.0.3 to 0.48 e Fur- 'ther, toravoid too great a' dilution of the hydrogen'sulbeing situated substantially at the longitudinal axis of said combustion zone, said pilot flame being maintained f by burning a mixture of a gaseous fuel with a small excess of oxygen, said excess being from about 0.02% to about 3% by volumel'of the hydrogen-sulfide supplied to said combustion zone; igniting the oxygen-containing mixture upon entry thereof into the combustion zone .7 and continuously discharging the, resulting combustion tide-containing gasis such that the final mixture contains 7 V 7 Of Oxygen P from about 0145 to about 0.55 volumes volume of hydrogen sulfide.

'4. 'Acprocessfor the production of sulfur from a gaseous mixture comprising hydrogen sulfide and vaporous hydrocarbons, said hydrocarbons composing no a more than about 10% by'volume of said mixture, comprising. the steps of continuously supplyingvto a whirl zonej substantially "all of said hydrogen sulfide-containing mixture aridsuflicientoxygen-containing gas to produce a mixture containing from about 0.45 to about 0.55 volumesof oxygen per volume ofthe hydrogen; sulfide; effecting intimate mixing of said-hydrogen-sulfide and .said oxy gen-containing gas by'whirling them together in said whirl" 7 zone; continuously flowing'the resulting gaseous'mixture from said whirl zone through 'an' annular opening into and. through a combustion zone as a stabilized annular rotating current within forwardyelocity greater than the 7 combustion propagation velocity of said oxygen-contain ing gaseousmixture; maintaining a' pilot flame directed j .in the same direction asthe oxygen-eontaining mixture is flowing, said pilot flame being situated at'the'end ,of said combustion zone at which said oxygen-containing mixture enters and substantially on thelongitudinal axis of said combu stion zone, by burning a mixture of a gaseousfuel with a small excess of oxygen, said excess being from about 0.02% to about 3% by volume, of the, hydregen sulfide supplied to said. combustion, zone; igniting sald' oxygen-containing mixture promptly uponitsj entry' into said combustion zone, thereby forming :withinfsaidi zoneannular vortices that carry flame gases back toward the'point at which said annular" flow "enters said combustion zone both within said annular current andbetween V said annular current and the side wall of said combustion zone for rapidlyheating saidmixture uponits entry into said zone and'promotingrapid combustion ofsaid oxygen-containing mixture at a temperature aboveabout 1000" .,'dis'charging the resulting combustion products 7 Q 9 containing sulfur and water vapor from the end of said combustion zone substantially opposite the point at which said annular flow enters said zone and rapidly cooling the discharged combustion products to condense the sulfur.

5. A process for the production of sulfur from a gaseous mixture comprising hydrogen sulfide and vaporous hydrocarbons, said hydrocarbons composing no more than about 10% by volume of said mixture, said process comprising the steps of continuously mixing said mixture with an oxygen-containing gas in such proportions that there is produced a gaseous mixture containing from about 0.45 to about 0.55 volumes of oxygen per volume of hydrogen sulfide; passing the resulting gaseous mixture as a stabilized rotating annular flow into and through an elongate free-space combustion zone which is substantially cylindrical in shape, the diameter of said zone being at least equal to about 0.8 but not greater than about 1.5 times the diameter of said zone,

the outer diameter of the annular current as it enters said zone being from about 0.15 to about 0.67 times the diameter of said zone, the forward velocity of said current being greater than the combustion propagation velocity of said mitxure; maintaining a forwardly directed pilot flame at the rear of said combustion zone situated substantially at the longitudinal axis of said zone by burning a mixture of a gaseous fuel with a small excess of oxygen, said excess being from about 0.02% to about 3% by volume of the hydrogen sulfide supplied to said combustion zone; igniting said mixture of hydrogen sulfide and oxygen-containing gas promptly upon entry into said combustion zone, thereby forming within said zone annular vortices that carry flame gases back toward the point at which said annular flow enters said zone both within said annular current and between said annular current and the side wall of said zone for rapidly heating said mixture upon its entry into said zone and promoting rapid combustion of saidmixture at a temperature above 1000 C.; discharging the resulting combustion products containing sulfur and water vapor from the end of said combustion zone substantially opposite the point at which said annular flow enters said zone; and rapidly cooling the discharged combustion products to condense the sulfur.

6. The process for the production of sulfur from hydrogen sulfide gas containing hydrogen sulfide as the major combustible and free from hydrocarbons in amounts greater than 10% by volume of the total combustibles comprising the steps of continuously mixing said gas with an oxygen-containing gas in proportions to produce a gaseous mixture containing from 0.45 to 0.55 volumes of oxygen for every 1 volume of hydrogen sulfide; imparting a rotary movement to the resulting mixture in a confined annular whirl zone; withdrawing the gaseous mixture from said zone continuously as an annular current and flowing it with a rotating motion through an annular channel of diminishing radius to increase the angular velocity thereof; discharging the accelerated rotating annular current at a high forward velocity suflicient to prevent flash-back through an annular slit in the rear wall of a combustion chamber having, in addition to said rear wall, a closed side wall and an open front end, said side wall having the shape of a surface of revolution coaxial with the axis of said annular slit and having a length from 0.8 to 1.5 times the inside diameter of the side wall near the front end of the chamher, said annular slit having an outer diameter from about 0.15 to 0.67 times the inside diameter of the side wall near said rear wall; maintaining a forwardly directed pilot flame at the rear of said combustion chamber situated substantially at the said axis by burning a mixture of a gaseous fuel with a small excess of oxygen, said excess being from about 0.02% to 3% by volume of the hydrogen sulfide supplied to the combustion chamber; initiating combustion of said mixture of hydrogen sulfide and oxygen-containing gas promptly upon emergence from said slit, thereby forming in the combustion chamber stabilizing vortices that carry flame gases back toward the rear wall both within said annular current and between the annular current and. the side wall of the combustion chamber for rapidly heating the mixture upon emergence from the slit and promoting rapid combustion at a temperature above 1000 C.; discharging the resulting combustion products containing sulfur and water vapor from the front end of the combustion chamber; and rapidly cooling the discharged combustion products to condense the sulfur.

References Cited in the file of this patent UNITED STATES PATENTS 2,200,529 Baehr et al. May 14, 1940 2,258,305 Stirlen Oct. 7, 1941 2,386,202 Fernelius Oct. 9, 1945 2,386,390 Fernelius et al. Oct. 9, 1945 2,413,714 Keeling Ian. 7, 1947 2,497,095 Nevins et al. Feb. 14, 1950 2,497,321 Pattinson et al. Feb. 14, 1950 2,515,845 Van Den Bussche July 18, 1950 2,534,792 Nevins et a1. Dec. 19, 1950 

1. A PROCESS FOR THE PRODUCTION OF SULFUR FROM A GASEOUS MIXTURE CONTAINING HYDROGEN SULFIDE AS THE MAJOR COMBUSTIBLE AND CONTAINING NOT MORE THAN ABOUT 10% BY VOLUME OF SAID GASEOUS MIXTURE OF HYDROCARBON MATERIALS, SAID PROCESS COMPRISING THE STEPS OF CONTINUOUSLY MIXING SAID GASEOUS MIXTURE WITH AN OXYGEN-CONTAINING GAS IN SUCH PROPORTIONS THAT THERE IS PRODUCED A GASEOUS MIXTURE CONTAINING FROM ABOUT 0.30 TO ABOUT 0.70 VOLUMES OF OXYGEN PER VOLUME OF HYDROGEN SULFIDE THEREIN, CONTINUOUSLY FLOWING THE OXYGEN-CONTAINING GASEOUS MIXTURE AS A STABILIZED ANNULAR CURRENT INTO AND THROUGH A FREE-SPACE, PERIPHERALLY CONFINED, ELONGATE COMBUSTION ZONE WITH A SUFFICIENT FORWARD VELOCITY TO PREVENT FLASHBACK, MAINTAINING IN SAID COMBUSTIOIN ZONE, AT THE END OF SAID ZONE AT WHICH SAID OXYGEN-CONTAINING MIXTURE ENTERS, A PILOT FRAME DIRECTED IN THE SAME DIRECTION AS THE OXYGEN-CONTAINING MIXTURE IS FLOWING, SAID PILOT FLAME BEING SITUATED SUBSTANTIALLY AT THE LONGITUDINAL AXIS OF SAID COMBUSTION ZONE, SAID PILOT FLAME BEING MAINTAINED BY BURNING A MIXTURE OF A GASEOUS FUEL WITH A SMALL EXCESS OF OXYGEN, SAID EXCESS BEING FROM ABOUT 0.02% TO ABOUT 3% BY VOLUME OF THE HYDROGEN-SULFIDE SUPPLIED TO SAID COMBUSTION ZONE; IGNITING THE OXYGEN-CONTAINING MIXTURE UPON ENTRY THEREOF INTO THE COMBUSTION ZONE AND CONTINUOUSLY DISCHARGING THE RESULTING COMBUSTION PRODUCTS FROM THE COMBUSTION ZONE. 